Bruine Kiekendieven Circus aeruginosus in het Deltagebied in 1979-94

During systematic censuses of breeding Avocets, plovers, gulls and terns in the Delta area in the southwestern Netherlands, Marsh Harriers were also registered. Numbers increased up to 1982 and stabilised during 1982-87, after which another increase was noticed during 1988-91. Presently, the Delta area holds 270 pairs, i.e. a substantial part of the Dutch population of 1370-1410 pairs (Figure 1, Appendix 1). Haringvliet, Biesbosch, Zuid-Beveland and Zeeuwsch-Vlaanderen are the most important breeding areas. Breeding habitats are creeks, (overgrown) saltmarshes and increasingly also arable land. Egdes of newly created fresh water basins hold relatively few pairs, probably because cattle causes disturbance of nest sites.